I just added a couple of added pictures and a corrected schematic to the original post.

The schematic was corrected to show a jumper on U6 to force the motherboard to think it is running at 33MHz, regardless of speed switch setting. I found if I didn't do this, the motherboard thought it was running at 25MHz when set to 50MHz. This caused VRAM errors on boot.

Added schematic for the homemade clock doubler.

The pictures show the completed installation._________________Turbo Color Slab, Tadpole P1000G and SS5

Ok, Iím trying to gather the parts and information to overclock my 33Mhz Turbo Color Slab. I have a few questions.

1. You swapped the MC88915 chip for a 100Mhz part. Would a faster part work, such as a 133Mhz or 160Mhz MC88915 chip?
2. Do you have a current source for the parts?
3. You mention the need for a ground plane PC board for the doubler circuit, do you have a current source for that?
4. Folks on several Amiga forums mention that Motorola made some 68040 40Mhz chips with a K63H &L88M mask that were die shrinks, and they supposedly ran cool to the touch, with no heat sink required. Would it be possible to run one of those at 66Mhz with proper cooling? What modifications/hardware would be required to attempt that? Do you think that other peripherals on the bus would run at that speed?

3. Doubler circuit card:
I used a custom modified model 9210 Surfboard for the circuit card: http://www.capitaladvanced.com/9210.htm I bought it from a local electronics store, Fry's. They have many distributors or you can order it from Digi-key http://www.digikey.com/ I used a piece of copper tape on the bottom for the ground plane.

4. A 40MHz 68040 would work. However, since it will be running at 50MHz, you will still need a cooling solution (i.e. heat sink and fan).

3. Doubler circuit card:
I used a custom modified model 9210 Surfboard for the circuit card: http://www.capitaladvanced.com/9210.htm I bought it from a local electronics store, Fry's. They have many distributors or you can order it from Digi-key http://www.digikey.com/ I used a piece of copper tape on the bottom for the ground plane.

4. A 40MHz 68040 would work. However, since it will be running at 50MHz, you will still need a cooling solution (i.e. heat sink and fan).

Good luck with your mod.

Hello: As we have a lot of new forum members and I have been asked if this was possible, I thought this thread should be resurrected , I've never seen it before awesome work! Best Regards Rob Blessin_________________Rob Blessin President computerpowwow ebay sales@blackholeinc.comhttp://www.blackholeinc.com
303-741-9998 Serving the NeXT Community since 2/9/93